Humanoids with distinctive ridged foreheads, best remembered for a plot to take over Starfleet using a psychotropic game that hooked the crew of the Enterprise.
The Ktarians are humanoids recognizable by the pronounced ridges across their foreheads. They are known throughout the Alpha Quadrant, with individuals seen in Starfleet circles and on worlds such as Risa.
In The Game, William T. Riker met the Ktarian woman Etana Jol on Risa, who gave him an electronic game worn over the eyes. Each success stimulated the pleasure centres of the brain, producing a powerful psychotropic addiction, and the game spread rapidly through the crew as part of a Ktarian scheme to gain control of the Enterprise and then Starfleet.
Wesley Crusher and Robin Lefler uncovered the plot after avoiding the game, and Data, repaired by Wesley, used flashing light to free the crew from its hold. Ktarians remained part of the wider galaxy afterwards: Naomi Wildman, born aboard Voyager, is half Ktarian through her father.